bio3 0910 lec2 controls cd ks
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Cell Cycle ControlsBiology 3 Kawashima
Philippine Science High SchoolSY 2009-2010
Key Terms and Concepts
• Checkpoints• Cyclins• Cyclin-dependent kinases
• Also known as “Restriction Point” in mammalian cells
• Cells that go through G1 usually complete the cell cycle
• Cells that do not receive the go-signal exit the cell cycle
• Quiescent non-dividing stage called G0 phase
G1 Checkpoint
YES NO
G1 checkpoint
Continue with G1 and proceed to S
Exit cycle; switch to nondividing state
• MPF or maturation promoting factor drives the cell past the G2
checkpoint• MPF is a protein complex
composed of cyclins and cyclin-dependent kinases (Cdk)
• Accumulated cyclin in G2
associate with cyclin-dependent kinases
G2 Checkpoint
• Ensures that chromosomes are properly attached to mitotic spindle (composed of microtubules)
• Anaphase promoting complex (APC) is inactive until kinetochores have interacted with microtubules
• Activation of APC indirectly triggers breakdown of cyclins
M Phase Checkpoint
External Signals Affect Regulation
Stimulate cell division
•PDGF
Inhibit cell division
•Density dependence•Anchorage dependence
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